Wormholes May Hold The Key To Solving Stephen Hawking's Black Hole Paradox

A physicist and two colleagues believe that wormholes may help work out a paradox proposed by Stephen Hawking in the 1970s. The paradox involves what happens to information once it falls into a black hole.

In the 1970s, Stephen Hawking argued against Einstein's theory of general relativity, that nothing that falls into a black hole can escape it. Hawking determined that black holes should emit radiation when quantum mechanics is considered. "This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet," explained Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences.

But, Hawking's theory led to a paradox that ultimately the black hole will dissipate completely, and thus so will any information concerning its contents. However, this contradicts a fundamental assumption of quantum physics that information cannot simply disappear from the Universe.

"This suggests that general relativity and quantum mechanics as they currently stand are inconsistent with each other," states Goto. "We have to find a unified framework for quantum gravity."

Many physicists think that the information escapes, encrypted somehow in the radiation. In order to study this, they calculate the entropy of the radiation, which measures how much information is lost from the perspective of someone outside the black hole. Physicist Don Page calculated in 1993 that if no information is lost, the entropy will primarily grow, but will drop to zero as the black hole disappears.

This led to yet another problem in that when physicists simply combine quantum mechanics with the standard description of a black hole in general relativity, Page looks to be incorrect—the entropy continually grows as the black hole shrinks, meaning information is lost.

The new study looks at how black holes imitate wormholes, and therefore providing a pathway out for information. A wormhole is a bridge connecting distant regions of the Universe. Goto explains that this is not a wormhole in the real world, but rather a way of mathematically computing the entropy of the radiation. He says, "A wormhole connects the interior of the black hole and the radiation outside, like a bridge."

Goto and his two colleagues performed a detailed analysis combining both the standard description and a wormhole picture. This matched Page's prediction, suggesting that physicists are correct to suspect that information is preserved even after a black hole's doom.

"We discovered a new spacetime geometry with a wormhole-like structure that had been overlooked in conventional computations," stated Goto. "Entropy computed using this new geometry gives a completely different result." He also added that "We still don't know the basic mechanism of how information is carried away by the radiation. We need a theory of quantum gravity."

Top Image Courtesy of NASA